Open AccessULF wave derived radiation belt radial diffusion coefficients
Author(s) -
Ozeke Louis G.,
Mann Ian R.,
Murphy Kyle R.,
Rae I. Jonathan,
Milling David K.,
Elkington Scot R.,
Chan Anthony A.,
Singer Howard J.
Publication year - 2012
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011ja017463
Subject(s) - physics , van allen radiation belt , electric field , computational physics , magnetic field , diffusion , van allen probes , electron , solar wind , magnetosphere , geophysics , quantum mechanics , thermodynamics
Waves in the ultra‐low‐frequency (ULF) band have frequencies which can be drift resonant with electrons in the outer radiation belt, suggesting the potential for strong interactions and enhanced radial diffusion. Previous radial diffusion coefficient models such as those presented by Brautigam and Albert (2000) have typically used semiempirical representations for both the ULF wave's electric and magnetic field power spectral densities (PSD) in space in the magnetic equatorial plane. In contrast, here we use ground‐ and space‐based observations of ULF wave power to characterize the electric and magnetic diffusion coefficients. Expressions for the electric field power spectral densities are derived from ground‐based magnetometer measurements of the magnetic field PSD, and in situ AMPTE and GOES spacecraft measurements are used to derive expressions for the compressional magnetic field PSD as functions of Kp, solar wind speed, and L‐shell. Magnetic PSD results measured on the ground are mapped along the field line to give the electric field PSD in the equatorial plane assuming a guided Alfvén wave solution and a thin sheet ionosphere. The ULF wave PSDs are then used to derive a set of new ULF‐wave driven diffusion coefficients. These new diffusion coefficients are compared to estimates of the electric and magnetic field diffusion coefficients made by Brautigam and Albert (2000) and Brautigam et al. (2005). Significantly, our results, derived explicitly from ULF wave observations, indicate that electric field diffusion is much more important than magnetic field diffusion in the transport and energization of the radiation belt electrons.